This invention relates to a hand-operated portable label printing machine and, more particularly, to a label printing machine with which various information, particularly in the form of bar code characters and corresponding numerals that are read optically, are clearly printed on labels, or the like. Such machines are operated to print labels and advance a label strip, by squeezing and releasing a hand lever, and the printed labels are peeled from a backing strip and are then applied on the surfaces of desired articles.
In a conventional portable label printing machine, a relatively stationary hand grip is formed at the rear part of the machine frame, and a hand operated lever is pivotally connected to the grip. A printing device is positioned forward of the hand lever and it is fixed to a yoke that is attached to the hand lever. When the hand lever and grip are squeezed and released, the printing pressure of the type face of the printing device against labels to be printed varies according to the strength of the hand lever squeezing and releasing. As a result, clear and consistent printing, particularly of bar code characters, has not always been attained.
Ordinary, perhaps indistinctly printed labels made by such label printing machines have been adequate because store customers have been able to visually read the imprinted prices, sizes, production dates and other information about commodities, and store and supermarket employees and cashiers have also been able to visually read the information on labels.
It has become desirable to adopt the so called POS (point of sales) system, utilizing electronic computers, in large supermarkets. The numerals and other visual indicia representing several bits of information about commodities are replaced by optical character, machine readable bar code characters. The bar code characters are printed on labels, and the printed labels are applied on several commodities.
Especially in the UPC (Universal Product Code) bar code, which code was established by the American Supermarket Institute, a large printing area and high precision printing are required. The bar codes on the labels are optically read by a stationary optical reader installed at the store chashier's counter.
Conventional portable label printing machines having the above described connected hand lever and yoke were tried for printing machine readable bar code characters. But, because the pressure applied in imprinting against the labels varies according to the strength of the squeezing and the releasing of the hand lever and the grip, the clarity of printed bar codes on labels also varies and the probability of the bar code characters being accurately machine read becomes quite low. Therefore, such portable label printing machines are not used in practice for imprinting bar code characters.
For printing precise readable characters, the label printing machines as well as the printing devices therein have become large and heavy. In addition, since a printing device is typically placed in the front part of the machine and the center of gravity of the machine is also closer to the front, it becomes quite difficult to print labels by squeezing and releasing the hand lever with one hand of an operator while applying the printed labels to the commodities that are carried in his other hand.